The goals of this prospective longitudinal study are to examine the etiologic determinants of changes in adolescent drug use and other problem behaviors and the consequences of drug use on the individual's functioning in a sample of Colombian youth. The proposed sample includes 1483 females and 1483 males, ages 12-17, and their parents. Based on four earlier studies, we anticipate obtaining at least 85 percent of 2966 adolescents and parents at follow-up. The study will attempt to accomplish the following: (1) To examine interrelations and interactions of personality, family, peers, ecological context, drug context, and cultural factors as they affect the course of drug use (i.e., onset, stability, change), delinquency, "precocious" sexual behavior, and specific AIDS- related behaviors in a sample of Colombian youth; (2) To study the consequences of early drug use on Colombian adolescent and young adult intra- and interpersonal functioning; and (3) To identify the risk and protective factors that can affect Colombian adolescents engaging in drug use or other problem behaviors. Individual interviews with the adolescent subjects will be conducted by trained interviewers at two points in time. Data will also be collected from the mothers. Scales with adequate psychometric properties measuring the independent variables will be developed from the interview schedules. The primary analytic techniques will be LISREL, hierarchical, and logistic regression. The significance of this study lies in its longitudinal design with in- depth, intrapsychic, interpersonal, cultural, and problem behavior data available on Colombian adolescents. This is the first time such data will be available for Colombian youth, especially for so large a sample at particular risk for problem behaviors. Knowledge of the particular risk factors for problem behaviors (including drug use) in Colombian adolescents, knowledge of the protective factors which help offset the risks for drug use and other problem behaviors, and knowledge of the consequences of drug use for psychosocial functioning are important for determining the foci and timing of effective prevention and treatment programs. This data is particularly important in Colombian youth, because of the importance of the production and distribution of illegal drugs in Colombia and the influence and proximity of the drug picture on the development of Colombian adolescents. We will also be in a position to contrast drug use and risk and protective factors affecting drug use in Colombian and American adolescents with potential prevention and treatment benefits for both groups.